August 15 is the 227th day of the year (228th in leap years). There are 138 days remaining until the end of the year.
- 1171: King Alfonso IX of León (d. 1230)
- 1769: Napoleon Bonaparte (d. 1821)
- 1950: Anne, Princess Royal
- 423: Flavius Honorius (b. 384)
- 465: Libius Severus
- 1038: King Stephen I of Hungary
- 1057: Macbeth, King of Scotland
- 1118: Alexios I Komnenos (b. 1048)
- 1196: Conrad II, Duke of Swabia (b. 1173)
- 1369: Philippa of Hainault
- 1528: Odet of Foix, Viscount of Lautrec (b. 1485)
- 982: Holy Roman Emperor Otto II is defeated by the Saracens in the battle of Capo Colonna, in Calabria.
- 1018: Byzantine general Eustathios Daphnomeles blinds and captures Ibatzes of Bulgaria by a ruse, thereby ending Bulgarian resistance against Emperor Basil II's conquest of Bulgaria.
- 1040: King Duncan I is killed in battle against his first cousin and rival Macbeth. The latter succeeds him as King of Scotland.
- 1057: King Macbeth is killed at the Battle of Lumphanan by the forces of Máel Coluim mac Donnchada.
- 1185: The cave city of Vardzia is consecrated by Queen Tamar of Georgia.
- 1281: Mongol invasion of Japan: The Mongolian fleet of Kublai Khan is destroyed by a "divine wind" for the second time in the Battle of Kōan.
- 1261: Michael VIII Palaiologos is crowned Byzantine emperor in Constantinople.
- 1430: Francesco Sforza, lord of Milan, conquers Lucca.
- 1461: The Empire of Trebizond surrenders to the forces of Mehmed II. This is regarded by some historians as the real end of the Byzantine Empire. Emperor David is exiled and later murdered.
- 1511: Afonso de Albuquerque of Portugal conquers Malacca, the capital of the Sultanate of Malacca.
- 1517: Seven Portuguese armed vessels led by Fernão Pires de Andrade meet Chinese officials at the Pearl River estuary.